JP2017214237A - Production method of calcium carbonate sintered body and calcium carbonate for producing calcium carbonate sintered body - Google Patents
Production method of calcium carbonate sintered body and calcium carbonate for producing calcium carbonate sintered body Download PDFInfo
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- calcium carbonate
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- sintered body
- size distribution
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 title claims abstract description 184
- 229910000019 calcium carbonate Inorganic materials 0.000 title claims abstract description 91
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
- 239000002245 particle Substances 0.000 claims abstract description 73
- 238000005245 sintering Methods 0.000 claims abstract description 42
- 238000009826 distribution Methods 0.000 claims abstract description 40
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 230000005540 biological transmission Effects 0.000 claims abstract description 13
- 238000002844 melting Methods 0.000 claims abstract description 8
- 230000008018 melting Effects 0.000 claims abstract description 8
- 238000000691 measurement method Methods 0.000 claims abstract description 7
- 238000000748 compression moulding Methods 0.000 claims abstract description 6
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 4
- 229910052700 potassium Inorganic materials 0.000 claims abstract description 4
- 239000011591 potassium Substances 0.000 claims abstract description 4
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 4
- 239000011734 sodium Substances 0.000 claims abstract description 4
- 238000000465 moulding Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 14
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 10
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 5
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 5
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 2
- 239000002671 adjuvant Substances 0.000 claims 1
- 239000012752 auxiliary agent Substances 0.000 abstract description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 abstract description 2
- 235000010216 calcium carbonate Nutrition 0.000 description 71
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 14
- 239000001569 carbon dioxide Substances 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 7
- 238000010304 firing Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 239000000843 powder Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000012188 paraffin wax Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000007088 Archimedes method Methods 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000013329 compounding Methods 0.000 description 2
- 238000004455 differential thermal analysis Methods 0.000 description 2
- 238000000462 isostatic pressing Methods 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 239000008267 milk Substances 0.000 description 2
- 210000004080 milk Anatomy 0.000 description 2
- 235000013336 milk Nutrition 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000011049 pearl Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
Landscapes
- Compositions Of Oxide Ceramics (AREA)
Abstract
Description
本発明は、炭酸カルシウム焼結体の製造方法及び炭酸カルシウム焼結体製造用炭酸カルシウムに関するものである。 The present invention relates to a method for producing a calcium carbonate sintered body and calcium carbonate for producing a calcium carbonate sintered body.
炭酸カルシウム焼結体は、人工真珠の成長核などへの応用が期待されており、その製造方法について種々研究されている。一般に焼結法により、高密度の焼結体を得るには、焼結前の成形体において、高密度を有する成形体を得ることが重要であり、また焼結後の高い寸法精度を得るためにも必要である。そのためは高い密度の成形体が得られる出発粉体が望まれる。従来の炭酸カルシウム焼結体の製造方法では、一般に、炭酸カルシウムと焼結助剤の混合物を静水圧プレスにより成形体とし、この成形体を炭酸ガス雰囲気中で焼結することにより製造されている（特許文献１及び非特許文献１）。 The calcium carbonate sintered body is expected to be applied to the growth nucleus of artificial pearls, and various researches have been conducted on its production method. In general, in order to obtain a high-density sintered body by a sintering method, it is important to obtain a molded body having a high density in a molded body before sintering, and to obtain high dimensional accuracy after sintering. Is also necessary. Therefore, a starting powder that can obtain a molded body having a high density is desired. In a conventional method for producing a calcium carbonate sintered body, it is generally produced by forming a mixture of calcium carbonate and a sintering aid into a molded body by isostatic pressing and sintering the molded body in a carbon dioxide atmosphere. (Patent Literature 1 and Non-Patent Literature 1).
従来の技術においては、炭酸カルシウムの粒子径に関し、特許文献１では０．５μｍ以下のものが好ましいと記載されているだけである。また、非特許文献１においては、粒子径０．１μｍ以下の一次粒子からなる平均粒子径３μｍの中空状二次粒子を用いて炭酸カルシウム焼結体が製造されている。また、炭酸カルシウム焼結体の密度の向上には、粉砕による二次粒子を破壊と中空部分を除去、一次粒子のみからなる炭酸カルシウムの合成が好ましいと記載されているだけである。 In the prior art, with respect to the particle diameter of calcium carbonate, Patent Document 1 only describes that 0.5 μm or less is preferable. Further, in Non-Patent Document 1, a calcium carbonate sintered body is manufactured using hollow secondary particles having an average particle diameter of 3 μm made of primary particles having a particle diameter of 0.1 μm or less. Moreover, it only describes that the synthesis of calcium carbonate consisting only of primary particles is preferable for improving the density of the calcium carbonate sintered body by breaking the secondary particles by grinding and removing the hollow portions.
以上のように、従来技術においては、炭酸カルシウムの粒子径分布については詳細に検討されていない。 As described above, in the prior art, the particle size distribution of calcium carbonate has not been studied in detail.
また、特許文献１及び非特許文献１では、炭酸カルシウムと焼結助剤の混合物の成形体を、静水圧プレスにより作製している。量産性、コストの観点からは、打錠成形のような成形方法が優れており、静水圧プレスで成形体を作製するのは、工業的に工程が複雑となり、コストが高くなるという問題を有する。 Moreover, in patent document 1 and nonpatent literature 1, the molded object of the mixture of a calcium carbonate and a sintering auxiliary agent is produced by the isostatic press. From the viewpoint of mass productivity and cost, a molding method such as tableting is excellent, and producing a molded body by an isostatic press has a problem that the process is industrially complicated and the cost is increased. .
本発明の目的は、静水圧プレスを用いなくとも、一軸成形のような簡易の成形方法でも高密度の成形体が得られ、なおかつ高密度の炭酸カルシウム焼結体を製造することができる炭酸カルシウム焼結体の製造方法及び炭酸カルシウム焼結体製造用炭酸カルシウムを提供することにある。 An object of the present invention is to provide a calcium carbonate capable of producing a high-density molded body by a simple molding method such as uniaxial molding without using an isostatic press, and capable of producing a high-density calcium carbonate sintered body. It is in providing the manufacturing method of a sintered compact, and the calcium carbonate for calcium carbonate sintered compact manufacture.
本発明の炭酸カルシウム焼結体の製造方法は、透過型電子顕微鏡観察により測定した粒子径分布における平均粒子径（Ｄ５０）が０．０５〜０．３０μｍの範囲内であり、レーザー回折式粒度分布測定法により測定した粒子径分布における９０％粒子径（Ｄ９０）が３μｍ以下であり、ＢＥＴ比表面積が５〜２５ｍ２／ｇである炭酸カルシウムと、リチウム、ナトリウム及びカリウムの内の少なくとも２種の炭酸塩を含み、かつ融点が５５０℃以下である焼結助剤を準備する工程と、焼結助剤が０．３〜３．０質量％となるように混合した炭酸カルシウムと焼結助剤の混合物を圧縮成形して成形体を作製する工程と、成形体を４００〜６００℃で焼結することにより、炭酸カルシウム焼結体を製造する工程とを備えることを特徴としている。 In the method for producing a calcium carbonate sintered body of the present invention, the average particle size (D 50 ) in the particle size distribution measured by transmission electron microscope observation is in the range of 0.05 to 0.30 μm, and the laser diffraction particle size Calcium carbonate having a 90% particle diameter (D 90 ) of 3 μm or less and a BET specific surface area of 5 to 25 m 2 / g, and at least 2 of lithium, sodium and potassium in a particle size distribution measured by a distribution measurement method A step of preparing a sintering aid containing a seed carbonate and a melting point of 550 ° C. or less, and calcium carbonate and sintering mixed so that the sintering aid is 0.3 to 3.0% by mass It is characterized by comprising a step of producing a molded body by compression-molding a mixture of auxiliaries and a step of producing a calcium carbonate sintered body by sintering the molded body at 400 to 600 ° C. .
本発明においては、圧縮成形が、一軸成形であることが好ましい。 In the present invention, the compression molding is preferably uniaxial molding.
本発明においては、成形体を空気中で焼結することが好ましい。 In the present invention, the molded body is preferably sintered in air.
本発明においては、焼結助剤が、炭酸カリウム及び炭酸リチウムの混合物であることが好ましい。 In the present invention, the sintering aid is preferably a mixture of potassium carbonate and lithium carbonate.
本発明においては、炭酸カルシウムが、純度９９質量％以上であることが好ましい。 In the present invention, the calcium carbonate preferably has a purity of 99% by mass or more.
本発明の炭酸カルシウム焼結体製造用炭酸カルシウムは、透過型電子顕微鏡観察により測定した粒子径分布における平均粒子径（Ｄ５０）が０．０５〜０．３０μｍの範囲内であり、レーザー回折式粒度分布測定法により測定した粒子径分布における９０％粒子径（Ｄ９０）が３μｍ以下であり、ＢＥＴ比表面積が５〜２５ｍ２／ｇであることを特徴としている。 The calcium carbonate for producing a calcium carbonate sintered body of the present invention has an average particle size (D 50 ) in a particle size distribution measured by transmission electron microscope observation in the range of 0.05 to 0.30 μm, and is a laser diffraction type. The 90% particle size (D 90 ) in the particle size distribution measured by the particle size distribution measurement method is 3 μm or less, and the BET specific surface area is 5 to 25 m 2 / g.
本発明によれば、密度の高い炭酸カルシウム焼結体を製造することができる。 According to the present invention, a high-density calcium carbonate sintered body can be produced.
以下、好ましい実施形態について説明する。但し、以下の実施形態は単なる例示であり、本発明は以下の実施形態に限定されるものではない。 Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments.
（炭酸カルシウム）
本発明において用いる炭酸カルシウムは、透過型電子顕微鏡観察により測定した粒子径分布における平均粒子径（Ｄ５０）が０．０５〜０．３０μｍの範囲内であり、好ましくは０．０８〜０．２５μｍの範囲内であり、さらに好ましくは０．１０〜０．２０μｍの範囲内である。平均粒子径（Ｄ５０）をこのような範囲内にすることにより、密度の高い成形体を作製することができ、密度の高い炭酸カルシウム焼結体を製造することができる。透過型電子顕微鏡観察による粒子径分布は、測定対象である炭酸カルシウムを透過型電子顕微鏡観察で１０００個以上測定することにより求めることができる。
(Calcium carbonate)
The calcium carbonate used in the present invention has an average particle size (D 50 ) in a particle size distribution measured by transmission electron microscope observation in the range of 0.05 to 0.30 μm, preferably 0.08 to 0.25 μm. And more preferably in the range of 0.10 to 0.20 μm. By setting the average particle diameter (D 50 ) within such a range, a molded body having a high density can be produced, and a calcium carbonate sintered body having a high density can be produced. The particle size distribution by observation with a transmission electron microscope can be obtained by measuring 1000 or more calcium carbonates to be measured by observation with a transmission electron microscope.
本発明において用いる炭酸カルシウムは、レーザー回折式粒度分布測定法により測定した粒子径分布における９０％粒子径（Ｄ９０）が３μｍ以下であり、好ましくは２．５μｍ以下であり、さらに好ましくは２．０μｍ以下である。レーザー回折式粒度分布測定法で粒子径分布を求めることにより、炭酸カルシウムの凝集体の粒子径分布を求めることができる。透過型電子顕微鏡観察により測定した粒子径分布における平均粒子径（Ｄ５０）が上記範囲内であり、レーザー回折式粒度分布測定法により測定した粒子径分布における９０％粒子径（Ｄ９０）が上記範囲である炭酸カルシウムは、粒子径分布がシャープであり、成形時の粉体のパッキング性に優れているので、高い密度の成形体を作製することができ、その結果密度の高い炭酸カルシウム焼結体を製造することができる。 The calcium carbonate used in the present invention has a 90% particle size (D 90 ) in a particle size distribution measured by a laser diffraction particle size distribution measuring method of 3 μm or less, preferably 2.5 μm or less, more preferably 2. 0 μm or less. By obtaining the particle size distribution by the laser diffraction particle size distribution measurement method, the particle size distribution of the calcium carbonate aggregate can be obtained. The average particle size (D 50 ) in the particle size distribution measured by transmission electron microscope observation is within the above range, and the 90% particle size (D 90 ) in the particle size distribution measured by the laser diffraction particle size distribution measuring method is the above. The range of calcium carbonate has a sharp particle size distribution and excellent powder packing at the time of molding, so a high-density molded body can be produced, resulting in high-density calcium carbonate sintering. The body can be manufactured.
また、本発明においては、透過型電子顕微鏡観察により測定した粒子径分布における１０％粒子径（Ｄ１０）に対する９０％粒子径（Ｄ９０）の比（Ｄ９０／Ｄ１０）が、２．３以下であることが好ましく、２．２以下であることがより好ましく、２．１以下であることがさらに好ましい。Ｄ９０／Ｄ１０がこのような範囲となることにより、粒子径分布がさらにシャープとなり、成形体及び炭酸カルシウム焼結体の密度をさらに高めることができる。 In the present invention, the ratio (D 90 / D 10 ) of 90% particle size (D 90 ) to 10% particle size (D 10 ) in the particle size distribution measured by transmission electron microscope observation is 2.3. Or less, more preferably 2.2 or less, and even more preferably 2.1 or less. By D 90 / D 10 is such a range, it becomes sharper particle size distribution, density of compacts and calcium carbonate sintered body can be further increased.
本発明において用いる炭酸カルシウムは、例えば、一般的に良く知られた石灰乳に炭酸ガスを吹き込んで反応させる炭酸ガス化合法により製造することができる。特に平均粒子径（Ｄ５０）が０．１μｍを超える粒子については特許第０９９５９２６号の製造方法に従い製造することができる。 The calcium carbonate used in the present invention can be produced, for example, by a carbon dioxide compounding method in which carbon dioxide gas is blown into and reacted with lime milk that is generally well known. In particular, particles having an average particle diameter (D 50 ) exceeding 0.1 μm can be produced according to the production method of Japanese Patent No. 099926.
本発明において用いる炭酸カルシウムのＢＥＴ比表面積は、５〜２５ｍ２／ｇであり、７〜２０ｍ２／ｇであることが好ましく、８〜１５ｍ２／ｇであることがさらに好ましい。ＢＥＴ比表面積を上記の範囲内にすることにより、炭酸カルシウムの焼結性を高めることができる。このため、密度の高い炭酸カルシウム焼結体を製造することができる。 BET specific surface area of the calcium carbonate used in the present invention is a 5~25m 2 / g, is preferably 7~20m 2 / g, more preferably from 8 to 15 m 2 / g. By setting the BET specific surface area within the above range, the sinterability of calcium carbonate can be enhanced. For this reason, a calcium carbonate sintered compact with a high density can be manufactured.
本発明において用いる炭酸カルシウムの純度は、９９質量％以上であることが好ましく、９９．５質量％以上であることがより好ましく、９９．７質量％以上であることがさらに好ましい。 The purity of the calcium carbonate used in the present invention is preferably 99% by mass or more, more preferably 99.5% by mass or more, and further preferably 99.7% by mass or more.
（焼結助剤）
本発明において用いる焼結助剤は、リチウム、ナトリウム及びカリウムの内の少なくとも２種の炭酸塩を含み、かつ融点が５５０℃以下である焼結助剤である。焼結助剤の融点は、５３０℃以下であることが好ましく、５２０〜４５０℃の範囲であることがさらに好ましい。焼結助剤の融点を上記範囲にすることにより、より低温で焼成して炭酸カルシウム焼結体を製造することができる。焼結助剤は、炭酸カリウム及び炭酸リチウムの混合物であることが好ましい。焼結助剤の融点は、例えば、相図から求めることができるし、示差熱分析（ＤＴＡ）により測定することも可能である。
(Sintering aid)
The sintering aid used in the present invention is a sintering aid containing at least two carbonates of lithium, sodium and potassium and having a melting point of 550 ° C. or lower. The melting point of the sintering aid is preferably 530 ° C. or less, and more preferably in the range of 520 to 450 ° C. By setting the melting point of the sintering aid in the above range, it is possible to produce a calcium carbonate sintered body by firing at a lower temperature. The sintering aid is preferably a mixture of potassium carbonate and lithium carbonate. The melting point of the sintering aid can be determined from a phase diagram, for example, or can be measured by differential thermal analysis (DTA).
（炭酸カルシウムと焼結助剤の混合物）
本発明においては、焼結助剤の含有割合が０．３〜３．０質量％となるように、炭酸カルシウムに焼結助剤を混合して混合物を調製する。焼結助剤の含有割合は、好ましくは０．４〜２．５質量％であり、さらに好ましくは０．５〜２．０質量％である。混合物中における焼結助剤の含有割合が少なすぎると、炭酸カルシウムを十分に焼結できない場合がある。焼結助剤の含有割合が多すぎると、炭酸カルシウム焼結体の密度を高めることができない場合がある。
(Mixture of calcium carbonate and sintering aid)
In the present invention, a mixture is prepared by mixing calcium carbonate with a sintering aid so that the content of the sintering aid is 0.3 to 3.0% by mass. The content ratio of the sintering aid is preferably 0.4 to 2.5% by mass, and more preferably 0.5 to 2.0% by mass. If the content of the sintering aid in the mixture is too small, the calcium carbonate may not be sufficiently sintered. If the content of the sintering aid is too large, the density of the calcium carbonate sintered body may not be increased.
（成形体）
本発明においては、上記混合物を圧縮成形して成形体を作製する。圧縮成形は、一軸成形であることが好ましい。本発明によれば、一軸成形による成形体を用いて、高い密度を有する炭酸カルシウム焼結体を製造することができる。しかしながら、本発明においては、一軸成形に限定されるものではなく、静水圧プレス成形、あるいはドクターブレード成形など他に知られた成形方法により成形体を作製してもよい。
(Molded body)
In the present invention, the mixture is compression molded to produce a molded body. The compression molding is preferably uniaxial molding. According to the present invention, a calcium carbonate sintered body having a high density can be produced using a molded body obtained by uniaxial molding. However, the present invention is not limited to uniaxial molding, and a molded body may be produced by other known molding methods such as isostatic press molding or doctor blade molding.
本発明において、成形体の相対密度は、５０％以上であることが好ましく、５５％以上であることがより好ましく、５８％以上であることがさらに好ましい。成形体の相対密度は、成形体のかさ密度を、炭酸カルシウムの理論密度（２．７１１ｇ／ｃｍ３）で割った値である。成形体のかさ密度は、後述するアルキメデス法により測定することができる。上記成形体の相対密度は、１９６．１Ｍｐａ（２０００ｋｇｆ／ｃｍ２）の成形圧で、一軸プレス成形したときに得られるものであることが好ましい。上記範囲の相対密度にすることにより、より高い密度の炭酸カルシウム焼結体を得ることができる。 In the present invention, the relative density of the molded body is preferably 50% or more, more preferably 55% or more, and further preferably 58% or more. The relative density of the compact is a value obtained by dividing the bulk density of the compact by the theoretical density of calcium carbonate (2.711 g / cm 3 ). The bulk density of the molded body can be measured by the Archimedes method described later. The relative density of the molded body is preferably obtained by uniaxial press molding at a molding pressure of 196.1 Mpa (2000 kgf / cm 2 ). By setting the relative density within the above range, a calcium carbonate sintered body having a higher density can be obtained.
（炭酸カルシウム焼結体の製造）
本発明においては、上記の成形体を４００〜６００℃で焼結することにより、炭酸カルシウム焼結体を製造する。より簡易な工程で焼結するという観点からは、焼結の際の雰囲気は、空気中であることが好ましい。しかしながら、本発明はこれに限定されるものではなく、従来と同様に、炭酸ガス雰囲気中、あるいは窒素ガスなどの不活性ガス雰囲気中で焼結してもよい。本発明によれば、空気中で焼結させても、高い密度を有する炭酸カルシウム焼結体を製造することができる。
(Manufacture of calcium carbonate sintered body)
In this invention, a calcium carbonate sintered compact is manufactured by sintering said molded object at 400-600 degreeC. From the viewpoint of sintering in a simpler process, the atmosphere during sintering is preferably in the air. However, the present invention is not limited to this, and it may be sintered in a carbon dioxide atmosphere or an inert gas atmosphere such as nitrogen gas as in the prior art. According to the present invention, a calcium carbonate sintered body having a high density can be produced even when sintered in air.
焼成温度が低すぎると、炭酸カルシウムが十分に焼結しない場合がある。焼成温度が高すぎると、炭酸カルシウムが分解し酸化カルシウムが生成しやすくなるため好ましくない。より好ましい焼成温度は、４２０〜５８０℃であり、さらに好ましくは４３０〜５７０℃である。 If the firing temperature is too low, the calcium carbonate may not be sufficiently sintered. If the firing temperature is too high, calcium carbonate is decomposed and calcium oxide is easily generated, which is not preferable. A more preferable firing temperature is 420 to 580 ° C, and further preferably 430 to 570 ° C.
以下、本発明に従う具体的な実施例を説明するが、本発明はこれらの実施例に限定されるものではない。 Specific examples according to the present invention will be described below, but the present invention is not limited to these examples.
（実施例１〜３及び比較例１〜３）
＜炭酸カルシウムの製造＞
表１に示す粒子径分布及びＢＥＴ比表面積を有する炭酸カルシウムを製造した。平均粒子径（Ｄ５０）が０．１μｍを超える粒子については、特許第０９９５９２６号の製造方法に従い製造した。それ以外については、石灰乳に炭酸ガスを吹き込んで反応させる一般的な炭酸ガス化合法により製造した。
(Examples 1-3 and Comparative Examples 1-3)
<Manufacture of calcium carbonate>
Calcium carbonate having a particle size distribution and a BET specific surface area shown in Table 1 was produced. Particles having an average particle diameter (D 50 ) exceeding 0.1 μm were produced according to the production method of Japanese Patent No. 099926. About other than that, it manufactured by the general carbon dioxide compounding method by which carbon dioxide gas was blown into lime milk and made to react.
＜透過電子顕微鏡観察による粒子径の測定＞
得られた炭酸カルシウムについて、透過型電子顕微鏡観察により粒子径分布を測定した。測定対象である炭酸カルシウム粒子について１５００個の粒子径を測定し、粒子径分布から平均粒子径（Ｄ５０）ならびにＤ９０、Ｄ１０を求めた。各炭酸カルシウムの平均粒子径（Ｄ５０）ならびにＤ９０、Ｄ１０、及びＤ９０／Ｄ１０の値を表１に示した。
<Measurement of particle diameter by transmission electron microscope observation>
About the obtained calcium carbonate, particle size distribution was measured by transmission electron microscope observation. The 1500 particle size was measured as a measurement target calcium carbonate particles was determined the average particle diameter (D 50) and D 90, D 10 from the particle size distribution. Table 1 shows the average particle diameter (D 50 ) and the values of D 90 , D 10 , and D 90 / D 10 of each calcium carbonate.
＜レーザー回折式粒度分布測定法による粒子径の測定＞
得られた炭酸カルシウムについて、レーザー回折式粒度分布測定法により粒子径分布を測定した。その具体的な測定方法は以下のように行なった。測定装置として（株）島津製作所製レーザー回折式粒度分布測定装置 ＳＡＬＤ−２０００Ｊを用い、０．２％ヘキサメタリン酸ナトリウム溶液１００ｍＬに試料１ｇを加えた後サンプラに投入し、規定の吸光度に達した後、超音波を１分間照射し測定を行った。その測定した粒子径分布から、平均粒子径（Ｄ５０）を求め、表１に示した。
<Measurement of particle diameter by laser diffraction particle size distribution measurement method>
About the obtained calcium carbonate, the particle size distribution was measured by the laser diffraction type particle size distribution measuring method. The specific measuring method was performed as follows. After using a laser diffraction particle size distribution analyzer SALD-2000J manufactured by Shimadzu Corporation as a measuring device, 1 g of a sample was added to 100 mL of 0.2% sodium hexametaphosphate solution, and then the sample had reached a specified absorbance. The measurement was performed by irradiating ultrasonic waves for 1 minute. The average particle size (D 50 ) was determined from the measured particle size distribution and shown in Table 1.
＜ＢＥＴ比表面積の測定＞
得られた炭酸カルシウムについて、ＢＥＴ比表面積を測定し、結果を表１に示した。
<Measurement of BET specific surface area>
For the obtained calcium carbonate, the BET specific surface area was measured, and the results are shown in Table 1.
また、得られた炭酸カルシウムについて、純度を測定したところ、いずれの炭酸カルシウムも９９．８％であった。 Moreover, when purity was measured about the obtained calcium carbonate, all calcium carbonate was 99.8%.
＜焼結助剤＞
焼結助剤として、炭酸カリウムと炭酸リチウムの混合物を用いた。混合割合は、モル比で、炭酸カリウム：炭酸リチウム＝３８：６２である。混合物の融点（共融温度）は、４８８℃である。
<Sintering aid>
A mixture of potassium carbonate and lithium carbonate was used as a sintering aid. The mixing ratio in terms of molar ratio is potassium carbonate: lithium carbonate = 38: 62. The melting point (eutectic temperature) of the mixture is 488 ° C.
＜成形体の作製＞
焼結助剤の含有量が１．２質量％となるように、焼結助剤と炭酸カルシウムとを混合した。この混合物を適量のジルコニアボールが入ったポリエチレン瓶に入れ、一晩乾式混合を行い、原料粉末とした。この原料粉末を円筒状の金型内に入れ、プレス機を用いて一軸プレス成形した。９８Ｍｐａ（１０００ｋｇｆ／ｃｍ２）の成形圧で１分間予備プレス成形した後、１９６．１Ｍｐａ（２０００ｋｇｆ／ｃｍ２）の成形圧で１分間プレス成形した。
<Production of molded body>
The sintering aid and calcium carbonate were mixed so that the content of the sintering aid was 1.2% by mass. This mixture was put into a polyethylene bottle containing an appropriate amount of zirconia balls, and dry-mixed overnight to obtain a raw material powder. This raw material powder was put into a cylindrical mold and uniaxial press-molded using a press. After preliminary press molding 1 minute at a molding pressure of 98Mpa (1000kgf / cm 2), and 1 minute press molding at a molding pressure of 196.1Mpa (2000kgf / cm 2).
＜成形体の焼成＞
得られた成形体を、空気中で４８０℃の温度で３時間焼成した。なお、４８０℃に達するまで毎分１０℃で昇温させた。この焼成により、炭酸カルシウム焼結体を得た。
<Baking of molded body>
The obtained molded body was fired in air at a temperature of 480 ° C. for 3 hours. In addition, it heated up at 10 degreeC / min until it reached 480 degreeC. By this firing, a calcium carbonate sintered body was obtained.
＜成形体および焼結体の密度の測定＞
アルキメデス法より成形体および焼結体のかさ密度ρb［ｇ／ｃｍ３］を求め、得られたかさ密度を炭酸カルシウムの理論密度（２．７１１ｇ／ｃｍ３）で割り、その相対密度を求めた。成形体および焼結体のかさ密度は、次のように求めた。先ず、成形体あるいは焼結体の試料の乾燥重量Ｗ１を測定し、湯煎したパラフィン中にその試料を１０分程度静置した後、取り出して常温になるまで冷やした。冷めた後にパラフィンを含有した試料の重量Ｗ２を測定した。その後、その試料の水中重量Ｗ３を測定し、下記の式より試料のかさ密度ρbを求めた。
<Measurement of density of molded body and sintered body>
The bulk density ρ b [g / cm 3 ] of the molded body and the sintered body is obtained by the Archimedes method, and the obtained bulk density is divided by the theoretical density of calcium carbonate (2.711 g / cm 3 ) to obtain the relative density. It was. The bulk density of the molded body and the sintered body was determined as follows. First, the dry weight W 1 of the sample of the molded body or the sintered body was measured, after the sample was allowed to stand for about 10 minutes in paraffin was hot water, cooled to a room temperature extraction. The weight W 2 of the sample containing the paraffin after cooled was measured. Thereafter, the underwater weight W 3 of the sample was measured, and the bulk density ρ b of the sample was obtained from the following formula.
かさ密度ρb［ｇ／ｃｍ３］＝Ｗ１ρW／（Ｗ2−Ｗ3）
ρW：水の密度［ｇ／ｃｍ３］
Ｗ１：試料の乾燥重量［ｇ］
Ｗ２：パラフィンを含有した試料の重量［ｇ］
Ｗ３：試料の水中重量［ｇ］
Bulk density ρ b [g / cm 3 ] = W 1 ρ W / (W 2 −W 3 )
ρ W : Water density [g / cm 3 ]
W 1 : Dry weight of sample [g]
W 2 : Weight of sample containing paraffin [g]
W 3 : Weight of sample in water [g]
成形体および焼結体のかさ密度及び相対密度を表１に示した。 Table 1 shows the bulk density and relative density of the molded body and the sintered body.
表１に示すように、本発明に従う実施例１〜３では、高い密度の成形体及び高い密度の炭酸カルシウム焼結体が得られている。これに対し、比較例１〜３では、高い密度の成形体及び高い密度の炭酸カルシウム焼結体が得られていない。比較例３に用いた炭酸カルシウムは、透過型電子顕微鏡観察により測定した粒子径分布における平均粒子径（Ｄ５０）が本発明の範囲内であるが、レーザー回折式粒度分布測定法により測定した粒子径分布における９０％粒子径（Ｄ９０）が本発明の範囲外である。このため、炭酸カルシウムのパッケージ性に優れておらず、高い密度の成形体及び高い密度の炭酸カルシウム焼結体を得ることができない。 As shown in Table 1, in Examples 1 to 3 according to the present invention, a high-density molded body and a high-density calcium carbonate sintered body are obtained. On the other hand, in Comparative Examples 1 to 3, a high-density molded body and a high-density calcium carbonate sintered body are not obtained. The calcium carbonate used in Comparative Example 3 has an average particle size (D 50 ) in the particle size distribution measured by transmission electron microscope observation within the range of the present invention, but the particles measured by the laser diffraction particle size distribution measuring method. The 90% particle size (D 90 ) in the size distribution is outside the scope of the present invention. For this reason, it is not excellent in the package property of calcium carbonate, and a high density molded body and a high density calcium carbonate sintered body cannot be obtained.
本発明によれば、静水圧プレス成形を用いずとも、高い密度の成形体及び高い密度の炭酸カルシウム焼結体を得ることができる。また、炭酸ガス雰囲気中で焼成する必要はなく、空気中の焼成で高い密度の炭酸カルシウム焼結体を得ることができる。 According to the present invention, a high-density molded body and a high-density calcium carbonate sintered body can be obtained without using isostatic pressing. Moreover, it is not necessary to fire in a carbon dioxide gas atmosphere, and a high-density calcium carbonate sintered body can be obtained by firing in air.
Claims (6)
前記焼結助剤が０．３〜３．０質量％となるように混合した前記炭酸カルシウムと前記焼結助剤の混合物を圧縮成形して成形体を作製する工程と、
前記成形体を４００〜６００℃で焼結することにより、炭酸カルシウム焼結体を製造する工程とを備える、炭酸カルシウム焼結体の製造方法。 90% particles in the particle size distribution measured by laser diffraction particle size distribution measurement method with an average particle size (D 50 ) in the particle size distribution measured by transmission electron microscope observation in the range of 0.05 to 0.30 μm It contains calcium carbonate having a diameter (D 90 ) of 3 μm or less and a BET specific surface area of 5 to 25 m 2 / g, and at least two carbonates of lithium, sodium and potassium, and has a melting point of 550 ° C. or less. A step of preparing a sintering aid which is
A step of compression-molding a mixture of the calcium carbonate and the sintering aid mixed so that the sintering aid is 0.3 to 3.0% by mass to produce a molded body;
The manufacturing method of a calcium carbonate sintered compact provided with the process of manufacturing a calcium carbonate sintered compact by sintering the said molded object at 400-600 degreeC.
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